DC1317A-H - Demo Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1317A-H
ACTIVE RESET ISOLATED 9-36V INPUT TO 48V @1.5A DC/DC POWER CONVERTER
LT1952-1
DESCRIPTION
Demonstration circuit 1317A-H is isolated input to
48V output 1/8th Brick footprint converter featuring
the LT®1952 switching controller with Active Reset
circuit. The Active Reset circuit can improve the efficiency in wide input voltage applications. Also, the
Active Reset allows the implementation of self-driven
synchronous secondary rectifiers in some applications.
The DC1317A-H (Figure 7) converts isolated 9V to
36V input to 48V output and provides over 1.5A of
output current depending on cooling. When determining the cooling requirements the actual input voltage
range and continuous maximum output current must
be taken into account. The converter operates at
150kHz with the peak efficiency greater than 90%.
The DC1317 can be easily modified to generate output voltages in the range from 0.6V to 48V. The output currents of DC1317A demo board are limited by
total output power of up to 150W. Demo boards
DC830A and DC677A are recommended for higher
output power levels of up to 500W.
The available versions of DC1317A are:
DC1317A-E, 36-72Vin to 5V, 12A
DC1317A-F, 9-36Vin to 3.3V, 22A
* DC1317A-F5, 9-36Vin to 5V, 20A
DC1317A-G, 9-36Vin to 12V, 8A
* DC1317A-G18, 9-36Vin to 18V, 5A
DC1317A-H, 9-36Vin to 48V, 1.5A
* The *DC1317A-G18 is a slightly modified design
featuring 18V @6A output. Please contact the LTC
factory for details.
The DC1317 circuit features soft-start which prevents
output voltage overshoot on startup or when recovering from overload condition.
The DC1317 has precise over-current protection circuit that allows for continuous operation under short
circuit conditions. The low power dissipation under
short circuit conditions insures high reliability even
during short circuits.
The LT1952 can be synchronized to an external clock
of up to 400kHz. Please refer to LT1952 data sheet for
design details and applications information.
DC1317A-A, 34-75Vin to 3.3V, 35A
DC1317A-B, 18-72Vin to 5V, 25A
Design files for this circuit board are avail
available.
Call the LTC factory.
DC1317A-C, 18-72Vin to 12V, 8A-12A
DC1317A-D, 18-72Vin to 24V, 5A
LT is a trademark of Linear Technology Corporation
Table 1. Performance Summary
PARAMETER
CONDITION
VALUE
Minimum Input Voltage
IOUT = 0A to 1.5A
9V
Maximum Input Voltage
IOUT = 0A to 5A
36V
VOUT
VIN = 9V to 36V, IOUT = 0A to 2A
48V ±3%
Typical Output Ripple VOUT
VIN = 18V to 72V, IOUT = 0A to 5A
100mVP–P
Nominal Switching Frequency
150kHz
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1317A-H
ACTIVE RESET ISOLATED 9-36V INPUT TO 48V @1.5A DC/DC POWER CONVERTER
QUICK START PROCEDURE
PROCEDURE
Demonstration circuit 1317 is easy to set up to evaluate the performance of LT1952-1 circuit. Refer to
Fig
Fig ure 1 for proper measurement equipment setup
and follow the procedure below:
NOTE: When measuring the input or output voltage
ripple, care must be taken to avoid a long ground lead
on the oscilloscope probe. Measure the input or output voltage ripple by touching the probe tip directly
across the Vin or Vout and GND terminals. See Figure
2. for proper scope probe technique.
1.
With power off, connect the input power supply to
Vin and GND. Make sure that the input power supply has sufficient current rating at minimum input
voltage for the required output load.
2.
Turn on the power at the input.
NOTE: Make sure that the input voltage does not
exceed 36V including transients.
3.
Check for the proper output voltage.
Vout = 48V.
If there is no output, temporarily disconnect the
load to make sure that the load is not set too high.
4.
Once the proper output voltage is established, adjust the load within the operating range and observe the output voltage regulation, ripple voltage,
efficiency and other parameters.
5.
The DC1317 is equipped with an output capacitor
CSYS (100uF) that approximates typical system
rail capacitance. If system board already has capacitance of similar value CSYS can be removed.
2
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1317A-H
ACTIVE RESET ISOLATED 9-36V INPUT TO 48V @1.5A DC/DC POWER CONVERTER
Figure 1. Proper Measurement Equipment Setup
Figure 2. Scope Probe Placement for Measuring Input or Output Rip
Rip ple
ACTIVE RESET CIRCUIT
The Active Reset circuit on DC1317A-H demo board
consists of a small P-Channel MOSFET Q13 and
reset capacitor C25. The MOSFET Q13 is used to
connect the reset capacitor across the transformer
T1 primary winding during the reset period when
Q1 MOSFET is off. The voltage across capacitor
C25 automatically adjusts with the duty cycle to
provide complete transformer reset under all operating conditions.
Also the active reset circuit shapes the reset voltage
into a square waveform that results in lower drain
voltages for Q1 and Q2 MOSFETs. The lower
MOSFET drain voltages allow lower voltage and
lower Rdson MOSFETs to be used. The MOSFETs
must be avalanche rated for the peak-reset voltage.
If non-avalanche rated MOSFETs are used a proper
drain voltage de-rating should be used.
The main benefit of active reset circuit in the case of
DC1317A-H demo board is high efficiency (shown
in Figure 3), wide input range, high power density
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1317A-H
ACTIVE RESET ISOLATED 9-36V INPUT TO 48V @1.5A DC/DC POWER CONVERTER
and small size. To achieve such high efficiency all of
the power components were carefully selected.
Please consult LT factory for assistance if any
changes to the circuit are required.
LT1952 Efficiency 12V in to 48V out
92%
Efficiency
90%
88%
86%
24V input
12V input
84%
0.0
0.4
0.8
1.2
1.6
2.0
Iout [A]
Figure 3. High efficiency of DC1317ADC1317A-H al
allows
the board to be used in thermally critical appliapplications. Up to 2A of output current can be
drawn with proper air flow.
Figure 5. Fast transient response of DC1317ADC1317A-H
is superior to many competing power modules
without the additional output capaci
capacitors.
SOFT START FUNCTION
The DC1317 features LT4430 opto coupler driver
that has soft start function which produces monotonic startup ramp shown if Figure 6. The rise time
of output voltage is controlled by capacitor C19.
Also, the soft-start function will prevent input current surges even with full load at the output.
OUTPUT LOAD STEP RESPONSE
RESPONSE
The load step response of DC1317A-H is very fast
even though relatively small amount of output capacitance is present (6.8uF ceramic and 33uF low
ESR electrolytic). This is thanks to fast error amplifier of LT4430, optimal amount of current slope
compensation of LT1952, fast opto coupler and fast
error amplifier of LT1952. If higher load steps need
to be handled more output capacitance can be
added in order to keep the voltage transients at the
desired level. The load step transients are shown in
Figure 5.
Figure 6. The LT4430 opto coupler driver proproduces monotonic output voltage rise at startup
without out
out put voltage overshoot.
overshoot.
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QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1317A-H
ACTIVE RESET ISOLATED 9-36V INPUT TO 48V @1.5A DC/DC POWER CONVERTER
DEBUGGING AND TESTING
TESTIN G
The DC1317 can easily be tested and debugged by
powering the bias circuit separately from the main
power circuit. To place DC1317 into debug mode
remove the resistor R1 and connect 12V, 100mA
power source to +Vb node (right side of R1). By
doing this, the primary PWM controller LT1952 can
be activated without the main primary power being
applied to +Vin.
case of C6. Please modify the reference designators in
your schematic to reflect the actual component used.
The following simple PCB layout rules should be helpful.
If possible use solid ground planes on layers 2 and
n-1. The ground planes will prevent the switching
noise from coupling into sensitive lines.
Place sensitive lines on the inner layers that will be
shielded by grounds on layers 2 and n-1.
To activate the LT4430 control circuit, feed 5V,
100mA power source into pin 1 of LT4430 controller via a diode.
Keep the loop formed by Q1, RCS1, Cin and T1 tight.
Once the primary and secondary controllers are
running the main power (+Vin) can be applied
slowly while observing the switching waveforms
and output voltage.
Keep noise sensitive nodes like SD/VSEC, ROSC, FB,
COMP, ISENSE, BLANK and DELAY as small as possible by placing the associated components close to the
LT1952 and LT4430 chips.
The input current supplying the power transformer
T1 should not exceeded 200mA without the output
load. If one of the MOSFETs is damaged, the input
current will exceed 200mA.
Use local vias for all components that connect to
ground planes.
PCB LAYOUT
The PCB layout should be carefully planned to avoid
potential noise problems. The PCB layout for DC1317A
can be used as a guide. Since demo board DC1317A
has 8 versions the PCB layout has optional components that can be removed. The schematic in figure 7
is showing the circuit without any optional components. Also, the circuit in figure 7 does not show any
zero-ohm resistors. Please consult the schematic on
page 7 to determine if any of the options should be
included in your PCB layout.
Keep the loop formed by Q2, Q3 and T1 tight.
Do not place any traces on the layers 2 and n-1 to
avoid ground planes from being compromised.
If the PCB layout has to be done on 2 or 4-layer PCB
try to stay close to the guidelines outlined above. Also,
maximize the ground connections between components by placing the components tight together.
Please contact LT factory for additional assistance.
Also, the PCB layout has a common schematic that is
used just for the layout. The PCB layout schematic is
not included in this quick start guide but it is included
with PCB design files.
Please note that the actual circuit schematic on page 7
shows the component values. The PCB layout schematic included with design files does not show the
component values.
In some cases, a different component like a diode is
used in a place holder for a capacitor such as in the
5
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1317A-H
ACTIVE RESET ISOLATED 9-36V INPUT TO 48V @1.5A DC/DC POWER CONVERTER
D2
BAS516
1.5mH
+Vin
2.2R
R11
10k
Cin1
Cin2
Cin3
6.8uF, 50V
-Vin
6
D5
PDZ10B
+Vout
*Q3
PDU540
10, 11
T1
D6
BAS516
G45R2-0324.006
SW0
U2
LTC4440-5
5
R10
Vu1
1
C3
1u
2
3
1
Vfb
2
R15
249k 3
R42
0R 4
5
SS
C10
0.1u
6
R22
7
13.3k
8
Comp
Sout
FB=1.23V Vin
Rosc
Out
Sync
PGND
MaxDC Delay
Vr=2.5V
OC
SD
Isense
GND
Blank
R28
143k
R32
143k
+Vr2
TG
Inp
TS
RJK0653
C5
2.2u
Rcs1
4
D9
PDZ7.5B
0.005R
Vu1
*R29
PMEG3002
R2
560k
16
R26
220R
Vu1
U4
LT4430
U6
PS2801-1
1
D10
14
Cu1
4.7u
BAT760
C16
0.22u
Vfb
C23
1uF
R20
470k
12
11
10
D11
BAS516
Sout
15
13
Q9
BCX55
43k
5
R23 2.4k
R9
47R
9
C13
.47u
SW0
Vcc
R27
470R
Opto
GND Comp
SS
FB
C19
1uF, X5R
6
5
4
C17
15n
R34
19.6k
R35
487k
+Vo1
R38
6.04k
C15
2.2nF, 2kV
Demo Board DC1317A-H schematic
R53
200R
* Please change the ref designator to reflect the symbol.
NOTE:
BAS516
Sout
R30
1.2k
R54
2.2R
D17
R33
158k
2
3
C11
3.3n
R24
22k
SS
+Vb
GND
6
U1
LT1952-1
R14
33K
Q12
BC856T
Boost
Q1
C25
33n, 200V
R13
22K
Vcc
Csys
33u, 63V, HVH
+
GND
2
+Vin
+Vo1
7, 8
*Q2
PDS3200
D3
BAS516
+Vr2
9V-36V Input
L1
HR-PQA2050-220-LTC
1
6.8uF, X7R
Q10
PBSS8110 Vu1
+Vb
R1
Co1
L2
+Vin
C33
Q13
Si9407
0.1u
R45
10k
C34
0.33u, 100V
This schematic shows only the components required for operation of -H version
of DC1317A demo board.
All optional components of DC1317A demo board have been removed.
Also, all zero-ohm resistors have been replaced with wires.
Please consult the full DC1317A-H schematic to decide if any of the optional
components should be included in your design.
D14
BAS516
6
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1317A-H
ACTIVE RESET ISOLATED 9-36V INPUT TO 48V @1.5A DC/DC POWER CONVERTER
7
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1317A-H
ACTIVE RESET ISOLATED 9-36V INPUT TO 48V @1.5A DC/DC POWER CONVERTER
8
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